Control mechanism

ABSTRACT

The invention provides a control mechanism for the advancing and withdrawal of a functioning part displaceable in a housing against or under the influence of a spring and for locking the part alternately in an advanced and withdrawn position. The mechanism is of a construction which enables it to be made relatively small and of a few parts, e.g. of injection molded plastic, so as to take up little space and is particularly suitable for use in a writing implement for advancing and withdrawing a writing cartridge within the housing of the implement.

States Patent Unite Bross 51 Apr.41,1972

[54] CONTROL MECHANISM [72] Inventor: Helmut Bross, Altenberg uber Nuremberg,

Germany [73] Assignee: J. Firms Jacob-Ritter KG, Brensbach/Odenwald, Germany [22] Filed: Feb. 14, 1968 [2]] Appl. No.: 705,328

[30] Foreign Application Priority Data July 22, 1967 Germany ..B 93619 Sept. 14, 1967 Germany ..B 94464 [52] US. Cl ..401/110 [51] ..B43k 5/16 [58] Field oiSearch ..401/109-111 [56] References Cited H 7 UNITED STATES PATENTS 3,137,276 6/1964 Weisser ..4( 1/11 l Hechtle ..401/1 10 Marynissen ..401/1 10 Primary ExaminerLawrence Charles Attorney-Spencer & Kaye [57] ABSTRACT The invention provides a control mechanism for the advancing and withdrawal of a functioning part displaceable in a housing against or under the influence of a spring and for locking the part alternately in an advanced and withdrawn position. The mechanism is of a construction which enables it to be made relatively small and of a few parts, e. g. of injection molded plastic, so as to take up little space and is particularly suitable for use in a writing implement for advancing and withdrawing a writing cartridge within the housing of the implement.

16 Claims, 14 Drawing Figures PATENTEDAPR 41912 SHEET 1 0F 2 ti NW FIG. 1

INVENTOF?! He! m: Brass By nmmy PATENTEDAPR 4 1912 SHEET 2 OF 2 INVENTOR Helmui Bross BY We fli'orn;

CONTROL MECHANISM The invention relates to a control mechanism for the advancing and withdrawal of a functioning part displaceable in a housing against or under the influence of a spring, and for locking the said part in the advanced or withdrawn position.

There is a great demand for such mechanisms, for example for the manufacturing of writing instruments, wherein a writing medium carrier, for example a cartridge, is arranged for longitudinal displacement within a housing, the point thereof projecting out of the housing in the advanced position (writing position) and being covered by the housing in the withdrawn position (inoperative position).

It is endeavoured to design these control mechanisms to be as simple as possible, so as to keep the manufacturing costs low, and for this reason the mechanism parts frequently consist of injection moulded plastics parts. In particular, the number of mechanism parts is to be as small as possible, so as to make simple assembly possible. Also the present invention is directed to the achievement of this object, and it is the object thereof to still further simplify the known control mechanisms without, thereby detrimentally influencing the reliability of the control function. At the same time, the mechanism is to take up little space.

The invention is discussed hereinbelow with reference to control mechanism designs for writing instruments. It may, however, also be applied to control mechanisms for other purposes, for example for electrical switching devices.

In the case of the control mechanism according to the invention, there is first of all provided a pressure actuating member which is mounted for displacement in a housing and the actuating end of which extends out of the housing, there being provided on the said actuating member control elements which, relatively to the central axis, extending in the displacement direction, of the pressure actuating member, are arranged at the same height and project radially from the body of the pressure actuating member, the control elements having an end which is near" to and far from the actuating end of the pressure actuating member and there being provided at the far end of the control elements at least one control face designed as a bevel face, the bevel face extending in the direction of a tangent of a circle the center point of which is located on the above-mentioned central axis of the pressure actuating member. Furthermore, in the control mechanism according to the invention, there are shaped on the inner wall of a housing part strip-like projections extending parallel, in spaced relationship, to the above-mentioned central axis of the pressure actuating member and having at their end remote from the actuating end of the pressure actuating member a bevelled control face extending in the same direction as the control faces of the control elements of the pressure actuating member and having furthermore, at their longitudinal sides, faces in which the control elements of the pressure actuating member engaging into the intermediate spaces between the strips are so guided over their entire displacement path that the pressure actuating member is secured against rotation, the control faces being disposed at the same level relatively to the above-mentioned central axis. The above-mentioned mechanism parts or the control faces provided thereon cooperate with a displaceable control member which is rotatable in the housing and displaceable in the direction of the abovementioned central axis of the pressure actuating member, there being provided on the said control member, in spaced relationship, control elements which, as seen from the actuating end of the pressure actuating member, are arranged behind the control elements of the pressure actuating member and which, relatively to the above-mentioned central axis, are disposed at the same height and project radially from the body of the control member and are formed, in their side facing the control faces of the control elements of the pressure actuating member, in each case with a notch in which, in the abovementioned advance position, the end of a strip carrying the control face engages, there being formed on each notch at least one bevelled control face co-operating with the control faces of the pressure actuating member and of the strips and extending in the same direction as the latter, the spacing between the control elements of the rotatable control member being so dimensioned that the above-mentioned strips are able to travel between the control elements. Furthermore, in the case of the mechanism according to the invention, at least one stop designed between the above-mentioned strips, on the inner side of the housing, is provided for the control elements of the rotatable control member travelling-in into the intermediate spaces between the strips, on transition from the above-mentioned advanced position into the above mentioned withdrawn position. Finally, there is provided also a spring in the housing, which said spring influences the rotatable control member in such manner that the control faces thereof are, on advance of the pressure actuating member, pressed against the control faces thereof and, on withdrawal of the pressure actuating member, pressed against the control faces of the strips, whereby, due to the pressing-on of the control faces of the rotatable control member against the control faces of the further mechanism parts, further-rotation of the rotatable control member is produced.

A multiplicity of embodiments of the control mechanism according to the invention, as used on a writing instrument, is shown in the drawings, wherein:

FIG. 1 shows an illustration, for the greater part sectioned, of the rearward part of a writing instrument equipped with a control mechanism according to the invention;

FIG. 2 shows a development of the parts, essential to the invention, of the control mechanism;

FIG. 3 shows a section through the rear part of the writing instrument housing;

FIG. 4 shows an elevational view of the rotatable control member;

FIG. 5 shows a view of the pressure actuating member according to the invention;

FIG. 6 shows a development of the parts which are essential to the invention of a further embodiment of the control mechanism;

FIG. 7 shows a partial elevation looking at the end face of the pressure pin, as used in the design according to FIG. 6;

FIG. 8 shows an elevational viewof the end face of the rotatable control member, as used with the embodiment according to FIG. 6;

FIG. 9 shows a development of the parts which are essential to the invention of a further form of embodiment;

FIG. 10 shows a partial elevation looking on the end face of the control member used with this embodiment;

FIG. 11 shows a diagrammatic partial lateral elevation of the pressure pin for the embodiment according to FIGS. 9 and 10;

FIGS. 12 and 13 show developments of further examples of embodiment; and

FIG. 14 shows an elevation of a form of embodiment which has been varied in respect of the association between the cartridge and the mechanism parts, as compared with the embodiment according to FIG. 1.

In the drawings, parts corresponding functionally to each other have been given the same reference numerals.

The fundamentally identical construction of the various designs is described first of all with reference to FIGS. 1 to 5.

Disposed in the rear part of the housing (designated 1 as a whole) of a writing instrument, for example a ball-point pen, is the writing cartridge 2 which has a collar 2' against which bears one end of a compression spring 3 the other end of which passes into abutment against a stop formed on the housing (not shown). Extending out of the rearward end of the housing is a pressure pin 4 having at its forward end a sleeveshaped section 5 (hereinafter called, for the sake of brevity, the support sleeve), from the outer side of which there projects a multiplicity of control or actuating elements 6 (FIG. 5 The pressure pin is mounted for longitudinal displacement in the housing.

The pressure pin co-operates with a sleeve-shaped control or actuating member 7 (FIG. 4), from the outer side of which control elements 8 project. The latter cooperate furthermore with strips 9, 10, which are of uniform width and which are shaped-on at the inner side of the housing 1, thus being in one piece therewith, or with bevelled control faces shaped at their forward end (FIG. 3). With this arrangement, short strips 9 alternate with long strips 10, the long strips extending further forwardly than the short strips. The peripheral spacing between the long strips 10 corresponds to the peripheral extent of the control elements 8 of the control member 7. The peripheral spacing between the control elements 8 corresponds to the peripheral extent of the strips 10. The peripheral spacing between the strips 9, 10 corresponds to the peripheral extent of the control element 6 of the pressure pin.

' In this way, it becomes possible to nest the parts 6, 8, 9 and 10 one within the other, on assembly, and this results in a substantial saving of space in the radial direction. The arrangement relatively to each other of the parts of the mechanism shown in FIGS. 3'to 5, in the assembled condition, is apparent from FIG. 1. In this connection, there is mounted for displacement in the two intermediate spaces 11, 12 formed between a short strip 9 and the two long strips 10 adjacent thereto (the width of the said intermediate spaces corresponding to that of the strips 9,10) in each case a control element 6 of the pressure pin 4 (FIG. 2). The surfaces provided at the longitudinal sides of the strips serve for guiding the control element 6. Due to this form of guiding, the pressure pin 4 is secured against rotation. The control member 7 is, on the other hand, longitudinally displaceable in the housing and mounted for rotation therein. The rear end of the cartridge 2 is introduced into the cavity in the control member 7 and is pressed by the spring 3 against the bottom of the cavity. Provided at the forward end of the control element 6 is a control face (designed as a bevelled part 13) extending tangentially to a circle the center point of which is located on the center axis of the pressure pin 4. The Support sleeve ends before the rear end of the control faces 3. Thus, there is formed between the axial edges of the control element 6 an interspace 16 into which the control elements 8 of the control member 7 are able to travel. The control elements 8 are formed, in their side facing the rear end of the housing, within each case one notch 17 on which there is formed, on the delimiting wall thereof disposed forwardly in the direction of rotation of the control member, a bevelled control face 18. A further control face'18, parallel thereto, is formed on that outer edge of the control member 8 which is disposed rearwardly in the direction of rotation of the control member 7. The control faces l8, 18 extend in the same direction as the control faces 13 of the control element 6 of the pressure pin 4.

Formed on the other delimiting wall of the notch 17 is a bevel portion 19 which extends oppositely to the control face 18 and which, in view of its function (to be discussed later), is designated a guiding-back face. A guiding-back face 19, extending parallel thereto, is disposed at that outer edge of the control element 8 which is located forwardly in the direction of rotation of the control member 7. By means of the notch 17, two teeth are provided on each control member 8 and, in this connection, it is also possible for one tooth to be truncated, as shown by line 20 in FIG. 2. Fundamentally, it is also adequate if a control element 6 engages in only one of the two intermediate spaces 11,12.

Provided at the forward end of the long strips is a control face 10 which is designed as a bevel face and which terminates in a point 10''. The control face 10' extends in the same direction as the control faces 13 and 18.

The above-described parts of the control mechanism cooperate in the following manner:

In the withdrawn position (inoperative position), the control elements 8 of the control member 7 are pushed, under the influence of the force of the spring 3, into the interspaces between the long strips 10, or as far as the short strips 9 will permit such movement, so that the said short strips serve as a stop for the control elements 8 in the withdrawn position. This position of the control elements 8 is designated A in FIG. 2. In this position, the control face 18 projects into the intermediate space 11 between the strips 10, 9 and does so with a peripheral (minimum) projection extent such that, on depression of the pressure pin in the direction of the arrow 21, it is on the one hand assured that the control faces 13 of the control element 6 slide off in the direction of the bottom of the groove 17 and, on the other hand, in the lowermost position (designated B in FIG. 2) of the control member 17, the control faces 18 project beyond the control faces 13 with a peripheral extending line a such that a part of the control faces 18 takes up its position below the control faces 10 of the strips 10. The sliding of the control faces 18 on the control faces 13 (arrow 22 in FIG. 2) and therewith the further-rotation of the control 'member 7 under the influence of the spring 3 is not able to take place until that instant at which the control elements 8, during the depression of the pressure pin 4 in the direction of the arrow 21, have entirely emerged out of the intermediate space between the long strips 10 adjacent each other in each specific case. When the control member 7 is in this position, whereupon the control element 8 bears, with its-detent notch 17, on the control tip 14 of the control element 6, and if the pressure pin is then released, then, under the influence of the spring 3, the control face 18 is pressed against the control face 10, the return-guiding of the control element 6 being brought about by the oblique return-guiding face 19 impinging against the tip 14 thereof (arrow 23 in FIG. 2). The (intermediate) position adopted meanwhile by the control member 8 is designated C in FIG. 2 and is shown, merely for reasons of draughtsmanship, in co-operation with the adjacent strip. Under the influence of the spring 3, the control face 18 slides down on the guide face 10 (arrow 22) until the control face 10 of the long strip 10 impinges on the bottom of the notch 17. The advanced position of the cartridge 2 is thus reached.

On repeating the depression of the pressure pin 4, the control faces 13 and 18 co-operate and, when this is followed by release of the pressure pin, the control faces 18' and 10' cooperate, whereby the control element 18 is guided back once again into the position A. On return of the control element 6, the tips thereof co-operate with the return-guiding face 19 of the control elements 8. In the withdrawn position, the long strips 10 are pushed through the intermediate spaces 26 between the control members 8.

The stops for the rearward position of the control element 6 of the pressure pin are formed by a roof-shaped step 24. The abutment end of the control element 6 is bevelled in correspondingly roof-like manner (FIG. 5). The wall thickness of the housing is smaller in the zone of the step 24 and in the axial prolongation 25 of the intermediate spaces 11, 12, than the wall thickness in the zone of the strips 9,10. This results in a saving of material and shorter cooling times in the injection mould.

As can be seen from FIG. 4, there-are provided on the control member 7 two forwardly extending prolongations 27 which, in the example of embodiment illustrated, extend from two approximately diametrically opposite control elements 8 and have at their free end a protuberance projecting radially outwardly. Instead of this, the projections 27 may extent outwardly, so that, on fitting the control member 7 into the housing 1, they are pressed (with production of a resilient storing force) against the housing inner wall, in a zone located before the ends of the strips 10.

In this way, falling-out of the control member 7, and therewith also of the pressure pin 4, from the housing is avoided, for as long as the cartridge 2 and the compression spring 3 have not yet been inserted. Also the already mentioned roof-like bevelling of the rear end of the control element 6 has the effect of simplifying assembly. When the pressure pin 4 is introduced into the rear housing part, the rear bevelled faces of the control element 6 readily slide off at the edges of the strips 9, 10, so that the control elements 6 would pass of their own accord into the intermediate spaces 11,12.

In the case of the examples of embodiment according to FIGS. 6 to 8, the strips 9, 10 are designed to be wider than the control element 6. The guiding-back faces 19, 19' are restricted, in respect of their radial extending line, to the face zone of the control elements 8 corresponding in axial projection to the end face of the support sleeve 5. With this arrangement, the guiding-back faces 19 extend peripherally into the intermediate spaces 26 between the control elements 8. The guiding-back face 19 covers over the notch 17. The control elements 6 are so designed that their control faces 13 and their edges 14 located at the tip extend inwardly in a zone 14" corresponding, in axial projection, with the end face of the support sleeve 5. In the zone 14", the control elements 6 cooperate with the guiding-back faces 19,19. With this embodiment, the guiding-back faces may be given a larger angle of inclination relatively to the central axis of the pressure pin than in the case of the example of embodiment according to FIGS. 1 to 5. In this way, the guiding-back of the pressure knob in the shifting phase is assisted.

In the case of the example of embodiment illustrated in FIGS. 9 to l l, the guiding-back faces 29 are formed not on the control member 7, but on the pressure pin 4. For this purpose, the support sleeve 5 is drawn forwardly as far as the tip 14 of the control element 6. The guiding-back face 29, which'extends oppositely to the control face 13, is formed by notches 36 in the end face of the support sleeve 5. The side 31 disposed opposite the guiding-back face 19 of a notch 36 extends in the same direction as the control face 13 and is designed as an inwardly directed prolongation of the control face 13. The faces 29 and 31 meet at the point 30. The notches 17 formed in the control member 8 are designed in the same way as in the case of the example of embodiment according to FIGS. 6 to 8, so that the apices 14 of the teeth of the control elements 8 co-operate with the guiding-back faces 29 at the end face of the support sleeve 5. This form of embodiment has the advantage that the radial extending line of the walls of the support sleeve 5 can be exploited for the formation of the guiding-back faces of the pressure pin, in this way saving space in the radial direction.

In the case of the example of embodiment illustrated in FIG. 12, the short strips 9 have been dispensed with. The interspace 32 formed between the long strips 10 is, in this case, completely filled, in the peripheral direction, by the control element 6 of the pressure pin 4. The back-stop for the control element 6 is formed by a strip 33 which extends into the intermediate space 32 and with which the control element 8 cooperates, but does so only indirectly, i.e., via the control element 6. Consequently, the strip 33 also limits the withdrawal movement of the control member 8. For the purpose of saving material or for diminishing the wall thickness of the housing, there are again groove-shaped recesses adjacent the strip 33. The design of the control face 13 and of the guiding-back face 29 on the control element 6 corresponds to the design shown in FIG. 11, with the only difference, that due to the widening of the control elements 6, the latter now participate in the formation of the guiding-back face 29. The form of embodiment shown in FIG. 12 has the special advantage that the design of the inner walls of the housing 1 and, in consequence of the reduction of half of the number of control elements, the design of the pressure pin is greatly simplified. In the case of the example of embodiment according to FIG. 13, the control element 8 has the same design as in the case of the example of embodiment according to FIGS. 6 and 8. Formed on the control element 6, which again completely fills the intermediate space 32 between the long strips 10, at the end of two projections delimiting the recess 16, on the control element 6, there is in each case a control or actuating face 13 extending over the end face of the support sleeve 5, so that the latter once again participates in the formation of the control faces 13. In the case of the example of embodiment according to FIG. 14, the cartridge is supported (in contradistinction to what takes place in the case of the example of embodiment according to FIG. 1) not against the control member 7 but against the pressure pin 4. For this purpose, the latter is connected with a rodshaped member 34 which projects out of its forward end face and has at its free end a collar 34 against which the rear cartridge end bears. On the other side of the collar 34, there abuts the lower end of a spring 35 the upper end of which bears against the rotatable control member 7, whereby its control elements 8 are pressed against the control elements 6 of the pressure pin 4. This form of embodiment has the advantage of specially easy operation of the control mechanism.

I claim:

1. Control mechanism for the advance and withdrawal of a functional part displaceable in a housing against or under the influence of a spring, and for locking the said part in advanced and withdrawn positions, such mechanism comprising a pressure actuating member which is displaceably mounted in said housing and has a central axis extending in the direction in which the member is displaceable; an actuating end to said pressure actuating member extending out of the housing; control elements provided on said pressure actuating member, such control elements being arranged at the same height relatively to said central axis of the pressure actuating member and projecting radially from the pressure actuating member, the control elements having a near and remote end relatively to said actuating end of the pressure actuating member; at least one control face provided at the remote end of the control elements and designed as a bevelled face which extends in the direction of a tangent to a circle, the centre of which is located on the said central axis of the pressure actuating member; strip-shaped projections formed internally on said housing and extending, in spaced relationship, parallel to the said central axis of the pressure actuating member with said control elements engaging in the spaces between the strip-shaped projections; a bevelled control face at the ends of said strip-shaped projections remote from the actuating end of the pressure actuating member, such bevelled control face extending in the same direction as the control face of the control elements of the pressure actuating member; guide faces at the longitudinal sides of said strip-shaped projections and on which the control elements are so guided over their entire displacement that the pressure actuating member is secured against rotation, the control faces being located at the same height relatively to the said central axis; a control member which is rotatable in the housing and displaceable in the direction of the said central axis of the pressure actuating member; control elements provided, in spaced relationship, on said control member and projecting radially therefrom, such control elements, as seen from the actuating end of the pressure actuating member, being arranged behind the control elements of the pressure actuating member and being disposed at the same height relatively to the said central axis, and having, on the sides thereof facing the control faces of the control elements of the actuating member, in each case a notch into which, in the advanced position, the end carrying the control face of a strip-shaped projection engages; at least one bevelled control face on each notch co-operating with the control faces of the pressure actuating member and of said strip-shaped projections and extending in the same direction as the latter, the spacing between the control elements of the rotatable control member being so dimensioned that the said strip-shaped projections are able to travel between the control elements; a stop formed between the said strip-shaped pro jections internally of the housing for the control elements of the rotatable control member travelling, on transition from the said advanced position into the said withdrawn position, into the interspaces between the strip-shaped projection; and a spring arranged in the housing and acting on the rotatable control member in such a manner that the control faces thereof, on the advance of the pressure actuating member, are pressed against the control faces of the latter and, on withdrawal of the pressure actuating member, are pressed against the control faces of the strip-shaped projections, whereby, due to the pressure of the control faces of the rotatable control member against the control faces of the further mechanism parts, further-rotation of the rotatable control member is achieved.

2. The control mechanism specified in claim 1, in which said strip-shaped projections have a spacing accommodating two of said control elements of the pressure actuating member, the mechanism further including, within each space between said strip-shaped projections, a further strip-shaped projection formed internally of the housing and extending parallel to said first mentioned strip-shaped projections, such further stripshaped projections having a spacing relatively to the first mentioned projections such that the control elements of the pressure actuating member are able to travel into the spaces formed between the first and further strip-shaped projections, the end of the further strip-shaped projections remote from the actuating end of the pressure actuating member being setback relatively to the remote end of the first mentioned projections to such an extent that, on abutment of the control elements of the rotating control member at the remote end of the further strip-shaped projections, the withdrawn position of the rotatable control member is reached.

3. The control mechanism specified in claim 2 and including a bevelled face at one end of each of said further strip-shaped projections, such bevelled face being directed in the same direction as the control faces of said control elements of the rotatable control member and positioned to be engaged by such control elements in the withdrawn position.

4. The control mechanism specified in claim 2, in which the first and further strip-shaped projections and the control elements of the pressure actuating member have the same width.

5. The control mechanism specified in claim 1, in which said strip-shaped projections have a spacing accommodating one of said control elements of the pressure actuating member and such elements are positioned to be engaged by the control elements of the rotatable control member in the withdrawn position thereof.

6. The control mechanism specified in claim 1, and including a sleeve-shaped part formed on said pressure actuating member and having an open end towards the rotatable control member, such part carrying the control elements of the pressure actuating member.

7. The control mechanism specified in claim 6 and including a sleeve-shaped body to said rotatable control member, such body fitting within the said sleeve-shaped part of the pressure actuating member for a distance sufficient to cause the control elements of the rotatable control member to abut against the control elements of the pressure actuating member.

8. The control mechanism specified in claim 6, in which the control faces of the control elements of the pressure actuating member and the edges at the apices of the said control faces, in the direction towards the central axis of the pressure actuating member, extend into a zone which, in axial projection, coincides with the open end of the sleeve-shaped part of the pressure actuating member.

9. The control mechanism specified in claim 6, in which the open end of the sleeve-shaped part of the pressure actuating member, as seen from the actuating end of such member, terminates before the control faces of the pressure actuating member, so that, between the actual edges of the control elepositely directed to that of said control faces and operative, on

release of the pressure actuating member from a depressed position, to engage against one of said control elements of the pressure actuating member to displace the latter into the withdrawn position.

11. The control mechanism specified in claim 10 in which said return guiding faces are formed on the notches of the control elements of the rotatable control member.

12. The control mechanism specified in claim 6 and including at least one bevelled return guiding face formed at the the side of each control element of the rotating control member facing the control elements of the pressure actuating member, such bevelled return guiding face having an angle of inclination oppositely directed to that of said control faces and operative, on release of the pressure actuating member from a depressed position, to engage against one of said central elements of the pressure actuating member to displace the latter into the withdrawn position, said return guiding faces being, in respect of their radially extending line relatively to the control axis of the pressure actuating member, restricted to that face zone of the control elements of the rotating control member which, in axial projection, coincides with the open end of the sleeve-shaped part of the pressure actuating member, the mechanism including further return guiding faces extending into the intermediate spaces between the control elements of the rotatable control member.

13. The control mechanism specified in claim 6 and including bevelled return guiding faces formed on the open end of the sleeve-shaped part of the pressure actuating member, the angle of inclination of said return guiding faces being oppositely directed to that of said control faces and being positioned to co-operate with the apices of the control elements of the rotatable control member in such manner that the apices, when the pressure actuating member is released, are pressed against the return guiding faces, so as to displace the pressure actuating member into the withdrawn position.

14. The control mechanism specified in claim 2, in which said first and further strip-shaped projections are wider than the control elements of the pressure actuating member.

15. The control mechanism specified in claim 1 in which each of said control elements of the pressure actuating member has an end facing the actuating end of the pressure actuating member of bevelled roof-shaped form.

16. The control mechanism specified in claim 1 and including, on the rotatable control member, projections which, in a zone located externally of the strip-shaped projections of the housing inner walls, are pressed so firmly against the latter that the rotatable control member is secured against droppingout from the housing. 

1. Control mechanism for the advance and withdrawal of a functional part displaceable in a housing against or under the influence of a spring, and for locking the said part in advanced and withdrawn positions, such mechanism comprising a pressure actuating member which is displaceably mounted in said housing and has a central axis extending in the direction in which the member is displaceable; an actuating end to said pressure actuating member extending out of the housing; control elements provided on said pressure actuating member, such control elements being arranged at the same height relatively to said central axis of the pressure actuating member and projecting radially from the pressure actuating member, the control elements having a ''''near'''' and ''''remote'''' end relatively to said actuating end of the pressure actuating member; at least one control face provided at the remote end of the control elements and designed as a bevelled face whicH extends in the direction of a tangent to a circle, the centre of which is located on the said central axis of the pressure actuating member; strip-shaped projections formed internally on said housing and extending, in spaced relationship, parallel to the said central axis of the pressure actuating member with said control elements engaging in the spaces between the strip-shaped projections; a bevelled control face at the ends of said strip-shaped projections remote from the actuating end of the pressure actuating member, such bevelled control face extending in the same direction as the control face of the control elements of the pressure actuating member; guide faces at the longitudinal sides of said strip-shaped projections and on which the control elements are so guided over their entire displacement that the pressure actuating member is secured against rotation, the control faces being located at the same height relatively to the said central axis; a control member which is rotatable in the housing and displaceable in the direction of the said central axis of the pressure actuating member; control elements provided, in spaced relationship, on said control member and projecting radially therefrom, such control elements, as seen from the actuating end of the pressure actuating member, being arranged behind the control elements of the pressure actuating member and being disposed at the same height relatively to the said central axis, and having, on the sides thereof facing the control faces of the control elements of the actuating member, in each case a notch into which, in the advanced position, the end carrying the control face of a stripshaped projection engages; at least one bevelled control face on each notch co-operating with the control faces of the pressure actuating member and of said strip-shaped projections and extending in the same direction as the latter, the spacing between the control elements of the rotatable control member being so dimensioned that the said strip-shaped projections are able to travel between the control elements; a stop formed between the said strip-shaped projections internally of the housing for the control elements of the rotatable control member travelling, on transition from the said advanced position into the said withdrawn position, into the interspaces between the strip-shaped projection; and a spring arranged in the housing and acting on the rotatable control member in such a manner that the control faces thereof, on the advance of the pressure actuating member, are pressed against the control faces of the latter and, on withdrawal of the pressure actuating member, are pressed against the control faces of the strip-shaped projections, whereby, due to the pressure of the control faces of the rotatable control member against the control faces of the further mechanism parts, further-rotation of the rotatable control member is achieved.
 2. The control mechanism specified in claim 1, in which said strip-shaped projections have a spacing accommodating two of said control elements of the pressure actuating member, the mechanism further including, within each space between said strip-shaped projections, a further strip-shaped projection formed internally of the housing and extending parallel to said first mentioned strip-shaped projections, such further strip-shaped projections having a spacing relatively to the first mentioned projections such that the control elements of the pressure actuating member are able to travel into the spaces formed between the first and further strip-shaped projections, the end of the further strip-shaped projections remote from the actuating end of the pressure actuating member being set-back relatively to the remote end of the first mentioned projections to such an extent that, on abutment of the control elements of the rotating control member at the remote end of the further strip-shaped projections, the withdrawn position of the rotatable control member is reached.
 3. The control mechanism specified in claIm 2 and including a bevelled face at one end of each of said further strip-shaped projections, such bevelled face being directed in the same direction as the control faces of said control elements of the rotatable control member and positioned to be engaged by such control elements in the withdrawn position.
 4. The control mechanism specified in claim 2, in which the first and further strip-shaped projections and the control elements of the pressure actuating member have the same width.
 5. The control mechanism specified in claim 1, in which said strip-shaped projections have a spacing accommodating one of said control elements of the pressure actuating member and such elements are positioned to be engaged by the control elements of the rotatable control member in the withdrawn position thereof.
 6. The control mechanism specified in claim 1, and including a sleeve-shaped part formed on said pressure actuating member and having an open end towards the rotatable control member, such part carrying the control elements of the pressure actuating member.
 7. The control mechanism specified in claim 6 and including a sleeve-shaped body to said rotatable control member, such body fitting within the said sleeve-shaped part of the pressure actuating member for a distance sufficient to cause the control elements of the rotatable control member to abut against the control elements of the pressure actuating member.
 8. The control mechanism specified in claim 6, in which the control faces of the control elements of the pressure actuating member and the edges at the apices of the said control faces, in the direction towards the central axis of the pressure actuating member, extend into a zone which, in axial projection, coincides with the open end of the sleeve-shaped part of the pressure actuating member.
 9. The control mechanism specified in claim 6, in which the open end of the sleeve-shaped part of the pressure actuating member, as seen from the actuating end of such member, terminates before the control faces of the pressure actuating member, so that, between the actual edges of the control elements of the pressure actuating member, an intermediate space is formed for the entry of parts of the control elements of the rotatable control member.
 10. The control mechanism specified in claim 1, and including at least one bevelled return guiding face formed at the side of each control element of the rotating control member facing the control elements of the pressure actuating member, such bevelled return guiding face having an angle of inclination oppositely directed to that of said control faces and operative, on release of the pressure actuating member from a depressed position, to engage against one of said control elements of the pressure actuating member to displace the latter into the withdrawn position.
 11. The control mechanism specified in claim 10 in which said return guiding faces are formed on the notches of the control elements of the rotatable control member.
 12. The control mechanism specified in claim 6 and including at least one bevelled return guiding face formed at the the side of each control element of the rotating control member facing the control elements of the pressure actuating member, such bevelled return guiding face having an angle of inclination oppositely directed to that of said control faces and operative, on release of the pressure actuating member from a depressed position, to engage against one of said central elements of the pressure actuating member to displace the latter into the withdrawn position, said return guiding faces being, in respect of their radially extending line relatively to the control axis of the pressure actuating member, restricted to that face zone of the control elements of the rotating control member which, in axial projection, coincides with the open end of the sleeve-shaped part of the pressure actuating member, the mechanism including further return guiding faces extending into the intermediate spaces Between the control elements of the rotatable control member.
 13. The control mechanism specified in claim 6 and including bevelled return guiding faces formed on the open end of the sleeve-shaped part of the pressure actuating member, the angle of inclination of said return guiding faces being oppositely directed to that of said control faces and being positioned to co-operate with the apices of the control elements of the rotatable control member in such manner that the apices, when the pressure actuating member is released, are pressed against the return guiding faces, so as to displace the pressure actuating member into the withdrawn position.
 14. The control mechanism specified in claim 2, in which said first and further strip-shaped projections are wider than the control elements of the pressure actuating member.
 15. The control mechanism specified in claim 1 in which each of said control elements of the pressure actuating member has an end facing the actuating end of the pressure actuating member of bevelled roof-shaped form.
 16. The control mechanism specified in claim 1 and including, on the rotatable control member, projections which, in a zone located externally of the strip-shaped projections of the housing inner walls, are pressed so firmly against the latter that the rotatable control member is secured against dropping-out from the housing. 